1,3-Bis[(6-methyl-2-pyrid­yl)meth­yl]imidazolium bromide

Ga Young Kim; Sang-Kyu Park; Dong-Heon Lee; Gyungse Park

doi:10.1107/S1600536809006710

. 2009 Feb 28;65(Pt 3):o637. doi: 10.1107/S1600536809006710

1,3-Bis[(6-methyl-2-pyridyl)methyl]imidazolium bromide

Ga Young Kim ^a, Sang-Kyu Park ^a, Dong-Heon Lee ^a,^*, Gyungse Park ^b,^*

PMCID: PMC2968481 PMID: 21582286

Abstract

The title compound, C₁₇H₁₉N₄ ⁺·Br⁻, is built up from 1,3-bis[(6-methyl-2-pyridinyl)methyl]imidazolium cations and bromide anions. Each of two 6-methyl-2-pyridyl rings is rotated out of the imidazole plane, making dihedral angles of 79.90 (9) and 86.40 (9)°. The packing is consolidated by aromatic π–π interactions between the pyridine rings of neighbouring molecules [centroid–centroid distance = 3.554 (2) Å] and by weak C—H⋯N and C—H⋯Br hydrogen bonds.

Related literature

For the synthesis of N-heterocyclic carbenes, see: Arduengo et al. (1991 ▶); Enders et al. (1996 ▶); Frenzel et al. (1999 ▶); Gardiner et al. (1999 ▶); Herrmann et al. (1998 ▶); McGuinness et al. (1998 ▶); Öfele (1968 ▶); Wanzlick & Schonherr (1968); Wanzlick & Schönherr (1968 ▶); Zhang & Trudell (2000 ▶). For related structures, see: Weskamp et al. (1999a ▶ b ▶).

Experimental

Crystal data

C₁₇H₁₉N₄ ⁺·Br⁻
M _r = 359.27
Monoclinic,
a = 8.2951 (4) Å
b = 12.4992 (5) Å
c = 16.1786 (7) Å
β = 95.709 (1)°
V = 1669.11 (13) Å³
Z = 4
Mo Kα radiation
μ = 2.47 mm⁻¹
T = 173 K
0.40 × 0.25 × 0.15 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.439, T _max = 0.709
10482 measured reflections
3923 independent reflections
2861 reflections with I > 2σ(I)
R _int = 0.070

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.094
S = 1.00
3923 reflections
201 parameters
H-atom parameters constrained
Δρ_max = 0.92 e Å⁻³
Δρ_min = −0.50 e Å⁻³

Data collection: SMART (Bruker, 1997 ▶); cell refinement: SAINT (Bruker, 1997 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809006710/lx2088sup1.cif

e-65-0o637-sup1.cif^{(19.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809006710/lx2088Isup2.hkl

e-65-0o637-Isup2.hkl^{(192.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C7—H7A⋯N4ⁱ	0.99	2.34	3.308 (4)	165
C7—H7B⋯Brⁱⁱ	0.99	2.79	3.660 (3)	147
C9—H9A⋯Br	0.95	2.91	3.695 (3)	141
C10—H10A⋯Brⁱ	0.95	2.68	3.521 (3)	148
C11—H11A⋯Br	0.99	2.93	3.801 (3)	147
C11—H11B⋯Brⁱ	0.99	2.89	3.690 (3)	138

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Symmetry codes: (i) Inline graphic ; (ii) .

supplementary crystallographic information

Comment

Many intensive researches have been focused on the synthesis of N-heterocyclic carbenes (NHCs) ligands due to their potential applications in important organic syntheses, such as Pd–catalysed Heck– and Suzuki–coupling, Co–catalysed ethylene copolymerisation, Ru–catalysed olefin metathesis and Rh–catalyse hydrosilylation (Frenzel et al., 1999; Enders et al., 1996; Gardiner et al., 1999; McGuinness et al., 1998; Weskamp et al., 1999a,b); Zhang & Trudell, 2000). We have interested in the use of tridentate N-heterocyclic carbene ligands. Here we report the crystal structure of the title compound, 1,3-bis[(6-methyl-2-pyridinyl)methyl]imidazolium bromide (Fig. 1).

The asymmetric unit of the title compound consists the C₁₇H₉N₄ cation and Br anion. Each of two 6–methylpyridine rings is rotated out of the imidazole plane, with dihedral angle of N1/C2–C6 of 79.90 (9)° and N4/C12–C16 of 86.40 (9)°, respectively. The crystal packing (Fig. 2) is stabilized by intermolecular aromatic π—π interactions between the pyridine rings of neighbouring molecules. The Cg—Cgⁱⁱⁱ distance of 3.554 (2) Å (Cg is the centroid of the N1/C2-C6 pyridine ring; symmetry code as in Fig. 2). The molecular packing is further stabilized by C—H···N interactions between the hydrogen of 7–methylene group and the N atom of pyridine ring of the neighbouring molecule, with a C7—H7A···N4ⁱ separation of 2.34 (1) Å (Table 1 and Fig. 2; symmetry code as in Fig. 2). Additionally, five different intermolecular C—H···Br hydrogen bonds in the structure are observed (Table 1 & Fig. 2).

Experimental

Synthesis of H(MepyCH₂)Im (1a): A mixture of imidazole (0.36 g, 6.0 mmol), 2-bromomethyl-6-methylpyridine (1.11 g, 6.0 mmol) and triethylamine (1.82 g, 1.8 mmol) in toluene (50 mL) was refluxed at 383 K for 10 h. After cooling, saturated aqueous NaHCO₃ solution was added and extracted with CH₂Cl₂ (3 x 20 mL). The combined organic fractions were dried over Na₂SO₄, filtered, and concentrated under reduced pressure to afford a dark colored solid in 53.0 % yield. Spectroscopic analysis: ¹H NMR(CDCl₃, 400MHz) : δ 7.62 (s, 1H, CH), 7.54 (t, 1H, J = 10 Hz, CH), 7.12 (s, 1H, CH), 7.09 (d, 1H, J = 1 Hz, CH), 6.99 (s, 1H, CH), 6.70 (d, 1H, J = 0.6Hz, CH), 5.21(s, 2H, CH₂), 2.56 (s, 3H, CH₃). ¹³C NMR (CDCl₃, 100MHz): δ 157.8, 154.1, 137.5, 136.6, 123.2, 122.5, 121.4, 118.9, 52.3, 23.9.

Synthesis of [H(MepyCH₂)₂-Im]Br (1): A mixture of (1a), H(MepyCH₂)Im, (0.52 g, 3.0 mmol) and 2-bromomethyl-6-methylpyridine (0.56 g, 3.0 mmol) in toluene (50 mL) was refluxed at 383 K for 14 h. After cooling, the solvents were removed by high-vacuum rotary evaporation. The residue was washed with Et₂O (5 x100 mL), and dried under the reduced pressure to afford a brown solid in 89.0 % yield. Single crystlas suitable for X-ray crystallography were obtained by Et₂O diffusion into a MeOH solution of the compound. Spectroscopic analysis: ¹H NMR (CDCl₃, 400 MHz) : δ 10.52 (s, 1H, CH), 7.66 (s, 2H, CH), 7.62 (t, 2H, J = 7.8 Hz), 7.54 (d, 2H, J = 7 Hz, CH), 7.14 (d, 2H, J = 7 Hz, CH), 5.65 (s, 4H, CH₂), 2.50 (s, 6H, CH₃). ¹³C NMR (CDCl₃, 100 MHz): δ 158.8, 151.3, 137.9, 137.3, 123.7, 122.1, 121.0, 54.2, 24.4.